In the production of oil shale by an in-situ heating process, multiple boreholes are placed in the ground and heat is applied for a period of years to convert the heavy oil or kerogen into lighter oil that will flow or be mobilized by water or steam to recovery boreholes.
One problem to be addressed is that after recovering the bulk of the oil the residual mobilized hydrocarbon liquids can become free to move in the subsurface and may contaminate groundwater. Barriers of clay and cement have been used to create subsurface barriers to groundwater movement. However, clay and cement cannot permeate most soil or rock. Creating an effective barrier generally requires removal of soil and rock material. This is a tedious task for depths over 100 feet. For oil shale recovery, the barriers may need to be up to a half mile deep. Placing the barriers is more difficult to control as depth increases. The barrier may need to extend through many formation layers of permeable and impermeable strata.
Freeze barrier of ice within the soil formation constructed by means of refrigeration pipes lowered into boreholes have also been used. A barrier may be needed to facilitate removal of groundwater within the perimeter of the barrier to improve heat distribution and prevent the mobilized hydrocarbon fluids and gas from migrating out of the heated zone. However, a freeze barrier may be ineffective in formations that do not contain sufficient water to form a barrier at all locations, are impermeable to water, or contain mostly hydrocarbons. A freeze barrier also may not be maintained in perpetuity to prevent environmental contamination. Even after final sweeping of the produced zone with water there will still be residual hydrocarbons in the lower permeability areas of the strata that can contaminate groundwater if the freeze barrier is removed.
As described in U.S. Pat. No. 5,879,110, historically, jets have been used to impinge upon and disrupt surrounding soil and insert wax and grout in combination with a synthetic liner. U.S. Pat. No. 5,879,110 is incorporated by reference in its entirety. This disruption to the surrounding soil is undesirable for large scale operations.
Thus, an impermeable subterranean barrier that is economical, environmentally sound, and effective is needed. An impermeable subterranean barrier that is formed using a system that does not depend on the disruption of subterranean formations which may have variable properties increases the reliability and potential depth range. A controlled and propagated permeation grouting in which the range of permeation of the grout is controlled by thermal preheating of the formation, rather than dictated by the local formation permeability, ease of disruption, or fracture properties is needed.